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Today some apps store big files over the internal SD card (e.g. games, podcasts, offline RSS content, pictures, videos, offline navigation software). Typically users have a small internal sd card size (~16GB) while the external SD is a lot bigger (~32-64GB). Most of these apps users download from the Play Store save their application data in the internal sdcard by default and don't have an option to use the external SD card to store data so they starve your internal SD card memory. FolderMount is the solution to this issue. This app has the ability to link folders in your internal sdcard to folders in your external sdcard thereby populating the internal sdcard folders with content that really exists in the external card. This helps us free space and have multiple games/apps with big data stored simultaneously without the need to uninstall. For Nexus devices with no external sdcard, this application should help link folders to a usb flash drive for example.

Features of FolderMount:

Mount internal SD card folders to external SD folders.

Move content from internal to external when a pair is added. (Dialog prompt)

Support for Android 2.3 - 5.0.

Holo themed throughout and an intuitive GUI design.

It will check SDCARD mount status and remount if necessary.

Purchase "pro" from within the app to unlock these limitations.

Howto

Add a folder pair. Source is the internal sdcard and destination is your extSdCard

After adding, FM will offer to move the files for you. Click yes.

Wait until the move operation is done then click on the PIN. If PIN turns green, you're all set.

The files will exist in both the source and destination after mounting. This is expected and is normal. The files you see in your internal sdcard actually reside in your external sdcard now and if you "unpin" the pair, you'll see that your internal sdcard is empty again.

There are other apps that do the same functionality but this is the first to bring you support for Android 4.2 with a Holo themed app and an intuitive interface.
Special thanks goes to Androidizen for creating the video promo of this app.
Have fun

Disclaimer: This app does not guarantee functionality in any way, shape, or form. It is not my responsibility if this app does not work, breaks your sdcard or eats your kittens. User discretion is advised.

What's New

Updated locales

Material design is finally here ! The migration to Material is a work-in-progress so there may be some traces of Holo here and there that will eventually all be ironed out with future releases.

NOTE: If you experience difficulties with downloading FolderMount Premium [ROOT] 2.8 APK from given links below, please try to login first to those file hosting before download (it's free to create an account), and then you can try to use UC Browser, you can download HERE (Direct Download)